'use client';

import { useControllableState } from '@radix-ui/react-use-controllable-state';
import { BrainIcon, ChevronDownIcon } from 'lucide-react';
import type { ComponentProps } from 'react';
import { createContext, memo, useContext, useEffect, useState } from 'react';
import { cn } from '../../utils';
import { Collapsible, CollapsibleContent, CollapsibleTrigger } from '../collapsible';
import { Response } from './response';

type ReasoningContextValue = {
    isStreaming: boolean;
    isOpen: boolean;
    setIsOpen: (open: boolean) => void;
    duration: number;
};

const ReasoningContext = createContext<ReasoningContextValue | null>(null);

const useReasoning = () => {
    const context = useContext(ReasoningContext);
    if (!context) {
        throw new Error('Reasoning components must be used within Reasoning');
    }
    return context;
};

export type ReasoningProps = ComponentProps<typeof Collapsible> & {
    isStreaming?: boolean;
    open?: boolean;
    defaultOpen?: boolean;
    onOpenChange?: (open: boolean) => void;
    duration?: number;
};

const AUTO_CLOSE_DELAY = 1000;
const MS_IN_S = 1000;

export const Reasoning = memo(
    ({
        className,
        isStreaming = false,
        open,
        defaultOpen = true,
        onOpenChange,
        duration: durationProp,
        children,
        ...props
    }: ReasoningProps) => {
        const [isOpen, setIsOpen] = useControllableState({
            prop: open,
            defaultProp: defaultOpen,
            onChange: onOpenChange,
        });
        const [duration, setDuration] = useControllableState({
            prop: durationProp,
            defaultProp: 0,
        });

        const [hasAutoClosed, setHasAutoClosed] = useState(false);
        const [startTime, setStartTime] = useState<number | null>(null);

        // Track duration when streaming starts and ends
        useEffect(() => {
            if (isStreaming) {
                if (startTime === null) {
                    setStartTime(Date.now());
                }
            } else if (startTime !== null) {
                setDuration(Math.ceil((Date.now() - startTime) / MS_IN_S));
                setStartTime(null);
            }
        }, [isStreaming, startTime, setDuration]);

        // Auto-open when streaming starts, auto-close when streaming ends (once only)
        useEffect(() => {
            if (defaultOpen && !isStreaming && isOpen && !hasAutoClosed) {
                // Add a small delay before closing to allow user to see the content
                const timer = setTimeout(() => {
                    setIsOpen(false);
                    setHasAutoClosed(true);
                }, AUTO_CLOSE_DELAY);

                return () => clearTimeout(timer);
            }
        }, [isStreaming, isOpen, defaultOpen, setIsOpen, hasAutoClosed]);

        const handleOpenChange = (newOpen: boolean) => {
            setIsOpen(newOpen);
        };

        return (
            <ReasoningContext.Provider value={{ isStreaming, isOpen, setIsOpen, duration }}>
                <Collapsible
                    className={cn('not-prose mb-4', className)}
                    onOpenChange={handleOpenChange}
                    open={isOpen}
                    {...props}
                >
                    {children}
                </Collapsible>
            </ReasoningContext.Provider>
        );
    },
);

export type ReasoningTriggerProps = ComponentProps<typeof CollapsibleTrigger>;

const getThinkingMessage = (isStreaming: boolean, duration?: number) => {
    if (isStreaming || duration === 0) {
        return <p>Reasoning...</p>;
    }
    if (duration === undefined) {
        return <p>Thought for a few seconds</p>;
    }
    return <p>Thought for {duration} seconds</p>;
};

export const ReasoningTrigger = memo(({ className, children, ...props }: ReasoningTriggerProps) => {
    const { isStreaming, isOpen, duration } = useReasoning();

    return (
        <CollapsibleTrigger
            className={cn(
                'flex w-full items-center gap-2 text-foreground-tertiary/80 text-xs transition-colors hover:text-foreground-tertiary',
                className,
            )}
            {...props}
        >
            {children ?? (
                <>
                    <BrainIcon className="size-4" />
                    {getThinkingMessage(isStreaming, duration)}
                    <ChevronDownIcon
                        className={cn(
                            'size-4 transition-transform',
                            isOpen ? 'rotate-180' : 'rotate-0',
                        )}
                    />
                </>
            )}
        </CollapsibleTrigger>
    );
});

export type ReasoningContentProps = ComponentProps<typeof CollapsibleContent> & {
    children: string;
};

export const ReasoningContent = memo(({ className, children, ...props }: ReasoningContentProps) => (
    <CollapsibleContent
        className={cn(
            'mt-4 text-sm',
            'data-[state=closed]:fade-out-0 data-[state=closed]:slide-out-to-top-2 data-[state=open]:slide-in-from-top-2 text-muted-foreground outline-none data-[state=closed]:animate-out data-[state=open]:animate-in',
            className,
        )}
        {...props}
    >
        <Response className="grid gap-2">{children}</Response>
    </CollapsibleContent>
));

Reasoning.displayName = 'Reasoning';
ReasoningTrigger.displayName = 'ReasoningTrigger';
ReasoningContent.displayName = 'ReasoningContent';
